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Implementation of Reflection on Curved Surfaces and Physical Optics in Ray Tracing for Tunnel Propagation
Yukiko KISHIKI Junichi TAKADA Gilbert Siy CHING Hajime TAKAO Yoshihiro SUGIHARA Shigeaki MATSUNAGA Fumiya UESAKA
Publication
IEICE TRANSACTIONS on Electronics
Vol.E96C
No.1
pp.4250 Publication Date: 2013/01/01 Online ISSN: 17451353
DOI: 10.1587/transele.E96.C.42 Print ISSN: 09168516 Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Electromagnetic Theory and Its Application) Category: Radiowave Propagation Keyword: ray tracing, physical optics, rough surfaces, curved reflection, tunnel propagation, caustics,
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Summary:
For the modeling of multipath propagation in every wireless systems, the ray tracing method has been widely studied. However, large errors may result due to the approximation of geometrical optics in curved surfaces. This paper therefore focused on the curved surfaces and edges, which are difficult to handle in ray tracing. Examples of curved surfaces can be found in arched crosssection tunnels which are common in highway networks of mountainous areas. The traditional ray tracing method of dividing the curved surface into smaller flat plates is not so accurate as the size of smaller plates may not satisfy the geometrical optics assumption, and the reflection point which satisfies Fermat's principle may not exist. In this work, a new ray tracing method is proposed with 2 contributions. The first one is the implementation of the reflection coefficient for curved surfaces in ray tracing. The second is applying the physical optics method on the caustics region. To evaluate these methods, path gain simulation results for an arched crosssection model are compared with measurements made inside an arched tunnel. To further improve the simulation results, the effect of rough surface is introduced, and the results are again compared with measurement.

